1. Field of the Invention
This invention relates to the recovery of sodium nitrilotriacetate monohydrate in solid particulate form from mixtures of NTA with water.
2. Description of the Prior Art
Typically sodium nitrilotriacetate monohydrate (NTA) is produced by chemical reaction in an aqueous solution. In use, frequently it is desired to provide product NTA in the form of a particulate mass of comparatively high bulk density and which is free flowing to permit handling and storage without excessive caking and lumping. Although NTA is produced readily in such desirable form by crystallization from solution and centrifugal separation of the crystals from the mother liquor, such processing involves a considerable amount of expensive equipment.
Spray drying of NTA solutions per se is an old technique. It is discussed in U.S. Pat. No. 3,409,666. The spray drying technique for producing particulate NTA from solutions was used in Germany during World War II. Unfortunately, the drying of NTA solutions in a spray dryer generally results in the production of a product comparable in some respects to damp snow in that it has a comparatively low bulk density and it does not flow readily when stored in silos and other bulk handling arrangements. Also it "cakes" excessively when packaged alone or in combination with other materials. Additionally, such material usually is very hygroscopic. Such product characteristics are obtained when feeding NTA solutions of various concentrations, even the more dilute solutions (10-15 wt. percent) which are known to produce spray dried products of a higher density when dealing with many other materials.